heverlee said:
..............there is a RC filter (R1-C1) used at the output of the 1st stage folded-cascode amplifier. This block indeed improves the compensation result. Can any one help explain me the principle of using this block to aid opamp compensation?
It´s a so called "snubber circuit" which, indeed, improves stability.
It introduces a pole as well as a zero (at a somewhat higher frequency) - thereby reducing loop gain at the upper frequency region (without making the slope of the loop gain steeper !) and thus improving phase margin.